JPS62153233A - Purification of 2-methylnaphthalene - Google Patents

Abstract

PURPOSE:2-Methylnaphthalene of high purity is obtained by distillation of a mixture of organic compounds containing 2-methylnaphthalene and 1- methylnaphthalene after addition of an alcanolamine such as monoethanolamine to the mixture. CONSTITUTION:An alkanolamine such as monoethanolamine is added to a mixture of organic compounds containing 2-methylnaphthalene and 1- methylnaphthalene such as coal tar fraction, after naphthalene fractionation, petroleum cracked oil or reformed oil, and the mixture is distilled to purify 2-methylnaphthalene. The amount of the monoethanolamine to be added to the mixture is at least 4 times that of the 2-methylnaphthalene included in the mixture. USE:A starting material for 2,6-naphthalenedicarboxylic acid which is used as an intermediate of vitamin K or polyester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to high-quality and efficient separation and acquisition of 2-methylnaphthalene from a mixture of organic compounds containing 1-methylnaphthalene and 2-methylnaphthalene. Regarding how to.

BACKGROUND TECHNOLOGY AND PROBLEMS 2-Methylnaphthalene is used as a raw material for vitamins, which are pharmaceuticals, and 2,6-7tale dicarboxylic acid, which is an intermediate raw material for the production of heat-resistant, high tensile strength polyester synthetic resins.
These are very important compounds, and when they are used as raw materials, it is important that they have a high degree of purity.In particular, 1-methylnaphthalene, which is closely related, and sulfur and nitrogen, which act as catalyst poisons and substances that reduce the reaction level, are important. The presence of impurities such as compounds must be eliminated at all costs.

Originally, 2-methylnaphthalene had a boiling point of 241.1'C.
* White crystals with a melting point of 34 and 4℃, coal tar.

It is contained in relatively large amounts in cracked petroleum oil. For example, the fractional distillate of coal tar is 7 and the talen oil is 6
~10% Single heavy oil contains about 3 to 6%, so 2-methylnaphthalene is usually separated by distillation or other means from these oils as raw materials.

By distillation, it is relatively easy to obtain a distillate containing 2-methylnaphthalene of 160% or more, but in this case, naphthalene, 1-
In addition to methylnaphthalene, it is inevitable that a large number of other components are mixed in, and at that level of purity, it cannot be used as a raw material for producing the vitamins mentioned above. If distillation separation is not technically applicable, crystallization separation is a common operation in chemical engineering, but in this case, 1-methylnaphthalene and 2-methylnaphthalene are
Since the latter composition of 17.5% creates a eutectic mixture, this measure cannot be applied either.

As a method that skillfully combines distillation and crystallization, for example, in JP-A-57-95923, 2-methylnaphthalene-containing oil is first reduced to a concentration of 60% or more in the naphthalene/2-methylnaphthalene weight ratio. A method for separating and recovering 2-methylnaphthalene is proposed, in which the 2-methylnaphthalene fraction is distilled to a value of 0.1 or less, and the resulting 2-methylnaphthalene fraction is continuously crystallized.

However, when using this method, the impurity methylbenzothiophenes, which have a melting point of about 36 to 52°C, are replaced with a melting point of about 34°C.
．． It is inevitable that it will be mixed into 2-methylnaphthalene at 4° C., and the purity of the product is limited to about 96%, and the yield of the product is only in the 50% range.

Furthermore, in JP-A No. 59-88432, a mixture of 1-methylnaphthalene and 2-methylnaphthalene is used as a full solution for a specific zeolite, that is, a zeolite with an aperture diameter of 6 Å or more.
Next, he teaches a method for chromatographic separation using tetralin or anisole as a developing agent. This method is not suitable for processing a large amount of material at once in terms of equipment, and this publication does not contain any description of the behavior of other contaminants other than methylnaphthalene, such as organic sulfur compounds and organic nitrogen compounds. do not have. Advanced purification of actual distillates
The separation method is questionable.

In any case, the development of means for separating and obtaining high-grade 2-methylnaphthalene from various fractions containing it has not yet been completed, and there is an urgent need to solve the problem.

Means for Solving the Problem The present invention has been made to solve the above problems, and includes adding monoethanolamine or alkanolamine to a mixture of organic compounds containing 2-methylnaphthalene and 1-methylnaphthalene, which are the materials to be purified. by adding
It is characterized by being subjected to distillation.

The mixture of organic compounds that is the material to be purified refers to a mixture of 2-methylnaphthalene and 1-methylnaphthalene, or an organic sulfur compound such as methylbenzothiophene, or an organic nitrogen compound such as pyridine, picoline, or indole. It refers to a mixture of organic compounds containing carbon, hydrogen, and/or nitrogen, and specifically includes various fractions of coal tar, cracked oil of petroleum, reformed oil, etc.

When these materials contain 7-talene,
It is desirable to distill this off in advance, but this will be discussed later.

This method of adding monoethanolamine to the material to be purified was discovered for the first time by the present inventors.

Soleha, monoethanolamine is naphthalene, 2-methylnaphthalene in the aforementioned material to be purified.

Compared to bicyclic aromatic hydrocarbons such as 1-methylnaphthalene, it has the property of extracting sulfur-containing, nitrogen-containing, and oxygen-containing heterocyclic compounds more selectively, and when heated, the temperature is near the boiling point of the amine. This is based on the discovery that its extraction ability is significantly expressed in

Also, monoethanolamine is naphthalene.

It has been found that it is azeotropic with bicyclic aromatic hydrocarbons such as methylnaphthalene and dimethylnaphthalene, but is difficult to azeotropically with heterocyclic compounds.

Moreover, it has been found that monoethanolamine has the property of azeotropically azeotroping more selectively with 2-methylnaphthalene than with 1-methylnaphthalene among the methylnaphthalene isomers.

On the other hand, among the two-ring aromatic hydrocarbons, naphthalene, methylnaphthalene isomers, and dimethylnaphthalene can be separated by a commonly known and common method of distillation. Therefore, when naphthalene and dimethylnaphthalene are contained in the mixture of organic compounds that are the materials to be purified, monoethanolamine is added after distilling off hetamine and dimethylnaphthalene in advance. If azeotropic distillation is carried out under pressure or reduced pressure, monoethanolamine and methylnaphthalene will azeotrope at a temperature near the boiling point of the amine, so if the fraction below the boiling point is distilled off, the impurity heterocyclic compound will be removed from the residue in the pot. As a result, highly pure 2-methylnaphthalene can be obtained.

The addition of monoethanolamine to the material to be purified is
Based on the amount of 2-methylnaphthalene contained in the material, it is preferable to add at least four times the amount (by weight). This is based on the experimental facts of the present inventors.

As shown in the examples, the fraction distilled as described above mainly consists of monoethanolamine and 2-methylnaphthalene, so this mixed fraction is cooled and precipitated. The crystals are separated by means such as centrifugation, and highly pure 2-methylnaphthalene is separated and obtained.

Since the selective extraction ability of naomonoethanolamine is understood to be based on its polarity, it is presumed to be common to alkanolamines, which are similar polar solvents.

Example 400.0g of monoethanolamine was added and mixed to 80p of mixed methylnaphthalene having the composition listed in Table 1, which is a mixture of various coal tar fractions, and the mixture was packed in a helipack filling type with 50 theoretical plates. Distillation was carried out using a distillation apparatus under normal pressure at a reflux ratio of 20:1. That is, the fraction having a boiling point of 171'C or less of the monoethanolamine was divided into nine fractions from the initial distillation.

The nine fractions collected here were cooled to 5°C, and the resulting crystals were collected by centrifugation. Second
The appearance indicates the chemical composition of these crystals, and the numerical values listed are gas chromatographic analysis values with the monoethanolamine cap removed.

Among these fractions, regarding the target 2-methylnaphthalene, the &1 to 8 fractions all show a high quality of 94% or higher. Therefore, we summarized these as crystal material 4.
I got 7.62 da.

This crystalline substance still has monoethanolamine attached to it, so after washing it with water at room temperature and drying it, the white 2
-47.05 g of methylnaphthalene crystals were obtained. The physical properties and chemical composition of this product are shown in Table 3, and the yield is 79.3% based on the mixed methylnaphthalene listed in Table 1.

Comparative Example 1 1 kg of the same mixed methylnaphthalene listed in Table 1 as used in the example was placed in a beaker, cooled to 5°C, and the precipitated crystals were centrifuged (filtered). 35001
1 m for 2 minutes), and crystalline product 354F was collected.

The physical properties and chemical composition of this crystal are shown in Table 4.

As shown, the purity of the 2-methylnaphthalene crystallized product from the first crystallization is 92.2%, but the yield is only 44.8%, and the undesirable impurities of 8% are 0 in total. .34%.

Next, this first crystallized crystal 35011 was taken, 350 g of ethanol with a purity of 99.5% was added thereto, and the mixture was dissolved at 30°C with stirring, then cooled to 5°C, and centrifugally filtered in the same manner as above. , thereby obtaining recrystallized product 193f. The physical properties and chemical composition of this product are also as shown in Table 4. The purity of 2-methylnaphthalene itself is 97.1%, but the total S is 0.29%.
The yield is only 25.7%.

Comparative Example 2 The same mixed methylnaphthalene 302. as used in the example.
71 was distilled under normal pressure at a reflux ratio of 20:1 using a Helipack packed distillation apparatus with 50 theoretical plates.The fraction of 2-methylnaphthalene with a boiling point of 242°C was divided into 10 fractions from the initial distillation. I stayed.

Table 5 shows the chemical composition of this fraction.

When these fractions &1 to 7 were combined, the purity of 2-methylnaphthalene was 90.1% recovered, 1i71.9%, and 0.45% for a total of 8 minutes, which was worse than the example.

Effects of the Invention According to the method of the present invention, as is clear from the Examples and Comparative Examples, high quality (low S) and high purity (98.0% The above 2-methylnaphthalene can be easily obtained. Moreover, as a distillation column, for example,
The number of theoretical plates is much smaller than that expected in the No. 219 invention, and it is considered to be extremely advantageous industrially.

Table 1 Table 3 Table 4

Claims (1)

[Claims] 1) A method for producing 2-methylnaphthalene, which is characterized by adding monoethanolamine or alkanolamines to a mixture of organic compounds containing 2-methylnaphthalene and 1-methylnaphthalene, and subjecting the mixture to distillation. Purification method 2) The method according to claim 1), wherein the mixture of organic compounds is a fraction of coal tar after naphthalene distillation, cracked petroleum oil, reformed oil, etc.